1. Field of the Invention
The present invention relates to radiation reflecting target surfaces, and more particularly to radar reflecting targets for returning impinging radar radiation in a path substantially parallel to the impinging beam.
2. Description of the Prior Art
More and more marine vessels are being launched and used in waters near or adjacent population dense areas. Frequently, in dense fogs, during exceptionally dark nights or in the turbulence of storms, even the best running lights appear terribly small and ineffective in a big ocean. Many if not most marine vessels are equipped with radar equipment adapted to inform the operator of nearby ships and structures in such circumstances.
Small and medium size sailboats and powerboats frequently are constructed of materials having almost no substantial surface area of radar reflecting characteristics. The hulls, decks and masts are frequently made of wood, fiberglass, or other plastic materials. Such small vessels can be absolutely invisible to radar detection.
In inclement weather or fog, most prudent sailors in crowded harbors and bays presently equip their vessel or boat with small, manually operated fog horns. Such horns have their usefulness, but reasonably cannot be expected to provide notice to large, ocean going vessels such as tankers, or to smaller vessels traveling at relatively high rates of speed and having substantial engine noise. To be "seen" by such vessels having radar equipment, it is highly desirable to have a radar reflecting target capable of being elevated and supported on a mast or perhaps secured over a rail. The height of the antenna above the water line determines the effective range of the radar which range is also affected by the height of the target vessel.
Several such radar targets or reflectors are currently available. The most effective of such targets attempts to utilize the well known corner or dihedral angle reflecting surface technique. For example, three mutually orthogonal planes, reflective on both sides and intersecting in a common point or vertex, frequently form the construction for such a reflector.
Such constructions, however, have been known to provide dangerously rough edges. In the past, such reflector targets have been known to damage masts and boat hulls. A substantially cylindrical reflector commercially available appears to claim a maze of prisms that would return signals at heeling angles of up to 35 degrees. Surprisingly, such arrangements apparently are ineffective.
It continues to be desired, therefore, to obtain a relatively small, yet highly reflective surface that will return radar radiation in paths substantially parallel to an impinging path. Moreover, it is extremely desirable to provide such a radiation reflector or target that can be attached easily to marine vessels without scarring or damaging the vessel or the operator.